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UNIVERSITY  OF  ILLINOIS 


Agricultural  Experiment  Station 


BULLETIN  No.  107 


COMPARATIVE  EXPERIMENTS 

WITH  VARIOUS  INSECTICIDES  FOR  THE 

SAN  JOSE  SCALE 


BY  S.  A.  FORBES 

STATE  ENTOMOLOGIST 


URBANA,  APRIL,  1906 


SUMMARY  OF  BULLETIN  No.  107. 

1.  Experiments  with  twenty-seven  different   kinds  and  forms  of  in- 
secticides for  the  San  Jose  scale  begun,  near  Richview.  111.,  in  January 
and  March,  1905.  Page  244. 

2.  Results  ascertained  by  careful  estimate  of  degree  of  infestation 
before  spraying,  the  last  of  May,  and  early  in  September.  Page  244. 

3.  Conditions  necessary  to  exact  experiment.  Page  245. 

4.  Special  purpose  of  operations,  to  compare  various  lime  and  sulphur 
mixtures  and  to  test  soluble  petroleum  preparations.  Page  246. 

5.  Most  general   results   establish  superiority    of   lime    and   sulphur 
washes  over  other  mixtures  tested,  and  of  late  spring  over  midwinter  appli- 
cations. Page  246. 

6.  Details  of  experiments  with  eleven  preparations  with  a  lime  and 
sulphur  basis.  Pages  247-254. 

7.  Tables  of  twenty  experiments.  Pages  253-254. 

8.  Eleven  principal  experiments  show  ratio  of  74  to  79  per  cent,  of 
benefit  with  the  lime  and  sulphur  solution  made  by  boiling,  without  salt  or 
blue  vitriol.  Page  255. 

9.  March  spraying  nearly  twice  as  effective  as  January  spraying. 

Page  256. 

10.     Soda  solutions  of  lime  and  sulphur  made  without  heat,  less  than 
half  as  efficient  as  boiled  .solutions  made  without  soda.  Page  256. 

•11.     Minor  experiments  with  lime  and  sulphur  mixtures,  and  with  miscel- 
laneous kerosene  insecticides,  confirm  conclusions  given  above.       Page  256. 

12.  Whale-oil  soap  found  about  equal  to  California  wash,  but  much 
more  costly.   Less  efficient  than  simple  lime  and  sulphur  solution.    Page  258. 

13.  Costs  of  various  materials  given.  .       Page  259. 

14.  Cheapest  as  well  as  most  efficient  insecticide,  is  lime  and  sulphur 
wash,  costing  84  cents  per  hundred  gallons.  Page  259. 

15.  General  summary  of  article.  Page  260. 


COMPARATIVE  EXPERIMENTS  WITH  VARIOUS  INSEC- 
TICIDES FOR  THE  SAN  JOSE  SCALE. 

In  my  Eleventh  Report  as  State  Entomologist,  published  in 
1903, 1  gave  the  results  of  experiments  and  extensive  practical  opera- 
tions with  several  of  the  more  prominent  insecticides  used  against  the 
San  Jose  scale,*  including  whale-oil  soap  solution,  hydrocyanic  acid 
gas,  kerosene  emulsion,  mechanical  mixtures  of  kerosene,  and  lime 
and  sulphur  compounds  known  as  the  "California  wash"  when  made 
with  the  addition  of  salt,  and  the  "Oregon  wash"  when  made 
with'  blue  vitriol.  All  these  substances  have  been  found  effective 
against  the  San  Jose  scale,  but  the  kerosene  mixtures  and  emulsions 
were  abandoned  by  me  in  December,  1901,  because  of  serious  dam- 
age done  to  trees  with  these  insecticides  in  1900  by  one  of  my  spray- 
ing parties,  working  under  the  immediate  personal  charge  of  my 
most  experienced  operator,  f  Crude  petroleum,  much  used  in  some 
other  states,  has  been  little  used  at  any  time  in  Illinois,  and  observa- 
tions made  by  one  of  my  assistants  in  1902  in  the  Catawba  Island 
district  in  northern  Ohio,  where  it  had  been  extensively  applied  by 
orchardists,  were  so  discouraging  that  I  have  made  but  a  single  ex- 
periment with  it.t 

After  the  passage  of  the  Illinois  inspection  law  in  1899  ^  be- 
came my  duty  to  treat,  free  of  expense  to  the  owner,  all  orchards  in- 
fested by  the  San  Jose  scale  which  there  was  good  reason  to  believe 
had  become  so  infested  before  the  passage  of  that  act.  As  it  has 
now  become  virtually  impossible  to  trace  existing  infestations  to  so 
remote  a  beginning,  this  feature  of  our  law  has  become  practically 
inoperative,  and  the  owner  is  required  to  treat  infested  trees  on  his 
own  account.  This  fact  has  made  if  important  that  every  effort 
should  be  made  to  distinguish,  among  the  various  available  insecti- 
cides, those  which  are  at  the  same  time  effective,  cheap,  and  conve- 
nient of  preparation  and  application,  especially  as  several  commercial 
compounds  of  lime  and  sulphur,  and  others  with  a  kerosene  basis, 
are  being  extensively  advertised  and  offered  in  condition  for  immedi- 

*Twenty-second  Rep.  State  Ent.  111.,  pp.  56-57,  89-90;  Bull.  80,  111.  Agr.  Exper.  Sta- 
tion, pp.  492-493. 

•(Twenty-second  Rep.  State  Ent.,  pp.  48-50. 
tlbid.,  pp.  93-95. 

243 


244  BULLETIN  No.  107.  [April, 

ate  application  when  diluted.  I  consequently,  last  winter,  instructed 
Mr.  E.  P.  Taylor,  the  assistant  in  charge  of  orchard  inspection  and 
insecticide  operations,  to  carry  on  a  series  of  experiments  in  a  care- 
fully chosen  orchard,  intended  to  test  a  number  of  these  insecticides 
under  identical  conditions  and  in  a  way  to  enable  us  to  give  the  re- 
sults in  the  exact  form  of  percentages  of  benefit  for  each. 

For  this  purpose,  control  was  obtained  of  two  small  orchards 
near  Richview,  111.,  both  belonging  to  Mr.  Edward  Tucker,  one  con- 
taining 780  apple-  and  peach-trees  badly  infested  in  the  main,  and  the 
other,  680  peach-trees  infested  throughout  but  much  less  heavily  so. 
These  orchards  were  divided  into  plots  of  varying  size,  those  in- 
tended for  the  more  important  insecticides  containing  from  47  to  141 
trees  each.  Minor  experiments  were  made  on  smaller  lots,  of  from 
3  to  33  trees,  and  single  trees  here  and  there  were  also  used  for  a 
few  preliminary  tests. 

Insecticides  were  applied,  partly  early  in  January,  from  the  3d 
to  the  loth,  and  partly  from  the  2ist  to  the  24th  of  March,  1905. 
Twenty-seven  kinds  and  forms  of  insecticides  were  used  in  all,  of 
which  seventeen  were  various  compounds  of  sulphur  and  lime,  six 
were  kerosene  preparations,  three  were  soap  solutions,  and  one  was  a 
simple  alkali.  The  results  were  tested  by  three  critical  examinations, 
one  made  January  3  and  4,  a  second  during  the  last  days  of  May,  and 
the  last  September  5  to  8.  It  is  of  course  impossible  to  get  an  accu- 
rate idea  of  the  effects  of  the  treatment  by  comparing  the  ratio  of 
living  to  dead  at  the  time  of  the  treatment  with  the  corresponding 
ratio  at  a  considerable  interval  thereafter,  unless  the  scales  remain 
attached  to  the  tree  after  death ;  and  that  they  gradually  disappear, 
especially  after  a  lime  and  sulphur  treatment,  was  shown  by  observa- 
tions reported  by  me  in  1902.* 

SYSTEM  OP  INSPECTION. 

The  choice  of  a  system  of  inspection  by  which  the  condition  of 
trees  treated  with  various  insecticides  could  be  compared  with  their 
condition  before  treatment,  and  with  that  of  other  trees  not  treated 
but  reserved  as  checks,  was  a  difficult  and  perplexing  matter.  At 
first  I  was  disposed  to  depend  mainly  on  counts  of  dead  and  living 
scales  from  various  parts  of  carefully  selected  trees,  from  which 
average  ratios  of  dead  to  living,  before  and  after  treatment,  might 
be  computed,  but  such  comparisons  rapidly  become  misleading  as 
the  scales  killed  by  the  spray  disappear  under  exposure  to  the 
weather.  Comparisons  of  the  results  of  treatment  with  different  in- 
secticides can  not  be  reliable  if  based  on  counts  of  living  and  dead, 

*Bull.  111.  Agr.  Exper.  Station,  No.  71,  p.  243. 


1906.}  EXPERIMENTS  WITH  SAN  JOSE  SCALE.  245 

because  the  scales  killed  by  one  insecticide  may  remain  longer  at- 
tached to  the  bafk  than  those  killed  by  another,  and  there  is  abundant 
evidence  that  this  is  often  the  case.  It  is  furthermore  practically 
impossible  to  make  sure  that  a  tree  selected  for  a  scale-count  is  a 
fair  average  of  its  plot  with  respect  to  the  degree  of  its  infestation, 
and  scarcely  less  difficult  to  make  sure  that  the  parts  of  its  infested 
surface  selected  for  counting  are  a  fair  average  for  the  tree.  For 
these  reasons  the  counting  method  was  abandoned,  in  the  main,  and 
I  have  relied  instead  upon  a  careful  estimate  of  degrees  of  infesta- 
tion for  each  tree  of  both  check  and  experimental  plots,  these  esti- 
mates being  recorded  in  figures  ranging  from  i  to  6.  From  these 
the  average  degrees  of  infestation  for  the  trees  of  each  plot  were  fig- 
ured, and  these  averages  were  compared  with  each  other  in  a  way 
to  show  numerically  the  effect  of  the  treatment  in  a  reduction  of  the 
average  amount  of  infestation. 

CONDITIONS  NECESSARY  TO  EXACT  EXPERIMENT. 

In  order  to  an  estimate  of  the  precise  value  of  the  results  here 
reported,  it  will  be  helpful  to  review  the  conditions  necessary  to  an 
entirely  satisfactory  experiment  of  this  description.  In  the  first 
place  one  should  have  at  his  command  an  orchard  of  considerable 
size,  either  all  of  one  variety  or  with  the  separate  varieties  planted 
in  complete  and  continuous  rows  all  running  in  one  direction.  This 
should  be  divided  across  its  whole  width,  and  across  the  variety 
rows,  into  strips  of  five  rows  each  if  moderately  infested  by  the  San 
Jose  scale,  and  into  seven  to  ten  rows  if  heavily  infested,  each  strip 
receiving  a  different  treatment  except  that  occasionally  strips  should 
be  left  untreated  as  checks.  To  avoid  the  mutual  influence  of  check 
and  experimental  plots  upon  each  other,  which  may  extend  from  one 
to  three  rows  in  each  direction  across  the  boundary,  only  the  interior 
rows  of  each  strip  should  be  used  for  comparison.  Experimental 
trees  near  the  borders  of  the  check  strip  are  likely  to  receive  young 
scales  from  the  latter  in  larger  number  than  they  lose,  if  the  experi- 
mental treatment  has  had  any  marked  effect,  and  the  reverse  is  of 
course  true  of  the  marginal  rows  of  the  check.  This  is  not  a  theoret- 
ical supposition  merely,  but  is  shown  by  our  previous  experience, 
and  by  some  of  the  averages  to  be  reported  farther  on.  As  the  check 
plots  will  act  as  centers  of  general  dispersal  of  the  scale  insects 
during  the  whole  of  the  following  season,  there  should  be  no  more 
of  them  than  are  clearly  necessary.  One  at  each  end  of  the  orchard 
will  usually  be  enough. 

The  trees  of  the  interior  rows  of  each  strip  should  be  graded  very 


246  BULLETIN  No.  107.  [April, 

carefully,  'one  by  one,  as  to  the  degree  of  their  infestation,  using, 
for  convenience,  a  scale  of  ten  degrees.  One  such  grading  should  be 
made  and  recorded  at  the  time  the  trees  are  sprayed,  another  about 
the  last  of  May,  just  as  the  young  are  beginning  to  appear,  and  a 
third  at  the  end  of  fall,  when  multiplication  of  the  scales  has  vir- 
tually ceased  for  the  season.  All  the  grading  should  be  done  by 
one  person,  or  by  two  persons  independently,  their  estimates  being 
averaged,  and  the  person  grading  the  infestation  should  not  know 
the  particulars  of  the  experimental  treatment. 

A  comparison  of  the  average  degrees  of  infestation  of  the  checks 
when  the  spray  is  applied,  and  again  in  May,  will  show  the  extent 
to  which  the  scales  may  have  died  during  the  interval,  under  the 
effects  of  weather  or  from  other  causes,  and  a  comparison  of  the  check 
and  experimental  plots,  respectively,  in  May,  will  show  the  immedi- 
ate effect  of  the  insecticide.  A  similar  comparison  of  these  two 
kinds  of  plots,  made  at  the  end  of  the  season  of  multiplication,  will 
show  the  ultimate  effect  of  the  treatment  at  the  end  of  the  year. 

ORIGINAL  PURPOSE  OE  OPERATIONS. 

Our  own  operations  were  originally  planned  with  special  refer- 
ence to  the  comparative  values  of  modifications  of  the  lime  and  sul- 
phur mixtures  proposed  by  various  entomologists,  and  also  as  a 
preliminary  test  of  the  efficiency  of  soluble  petroleums,  lime  and  sul- 
phur solutions,  and  other  ready-made  commercial  products  fre- 
quently offered  for  sale.  Reports  made  by  my  field  parties  of  the 
partial  failure  of  midwinter  sprayings  with  the  lime  and  sulphur 
washes  led  me  also  to  provide  for  a  careful  test  of  the  final  effect  of 
sprays  applied  in  January  as  compared  with  those  applied  in  March. 
i 

MOST  GENERAL  RESULTS. 

The  main  general  outcome  of  these  experiments  was  to  establish 
still  more  firmly  the  lime  and  sulphur  washes  as  superior,  on  the 
whole,  to  all  the  other  mixtures  tested,  and  to  show  that  January 
applications  of  these  preparations  have  scarcely  more  than  half  the 
final  effect  of  applications  made  in  March.  Among  the  lime  and  sul- 
phur mixtures,  those  made  without  salt  or  blue  vitriol  seemed  clearly 
more  efficient,  as  insecticides,  than  the  older  forms  containing  those 
substances,  and  the  solutions  made  with  soda,  without  boiling,  were 
the  least  efficient  of  all. 


1906.]  EXPERIMENTS  WITH  SAN  JOSE  SCALE.  247 

THE  LIME  AND  SULPHUR  MIXTURES. 

Seventeen  preparations  with  a  lime  and  sulphur  basis  were  used 
in  these  experiments.  They  included  various  forms  of  the  "Cali- 
fornia wash"  and  the  "Oregon  wash,"  and  mixtures  of  lime  and  sul- 
phur without  the  salt  necessary  to  the  former  or  the  blue  vitriol  neces- 
sary to  the  latter.  These  preparations  varied  in  the  kind  of  lime 
used  in  making  them,  in  the  proportions  of  the  various  ingredients, 
and  in  the  length  of  time  during  which  the  mixtures  were  boiled  to 
procure  the  solution.  Two  compounds  purporting  to  be  ready-made 
solutions  of  lime  and  sulphur  were  used,  known  respectively  as  "Cal- 
cothion"  and  "Con  Sol." 

Major  Experiments. — Eleven  of  these  experiments,  in  which 
more  than  50  trees  were  treated,  will  be  reported  first,  in  the  order 
of  their  final  effectiveness. 

1.  This  was  a  lime  and  sulphur  wash  made  of  15  pounds  of  Mar- 
blehead  lump-lime  and  an  equal  weight  of  sulphur  to  50  gallons  of 
water.    The  sulphur  was  first  put  into  12  gallons  of  water  nearly  at 
the  boiling  point,  after  being  mixed  with  enough  water  to  form  a 
thin  paste.    The  lime  was  then  added  and  the  mixture  was  boiled  for 
40  minutes  with  the  necessary  stirring.     The  whole  was  strained 
into  a  5o-gallon  tank  which  was  then  filled  with  water. 

Fifty-one  trees  were  treated  March  22,  1905,  in  the  less-infested 
orchard  (Orchard  II.),  at%a  sufficient  distance  from  the  check  strip 
to  prevent  any  possible  spread  of  the  young  scales  to  the  experi- 
mental plot.  The  trees  on  this  plot  were  compared  September  10 
with  those  in  the  two  central  rows  of  the  check  plot — which  was  six 
rows  wide — both  being  carefully  graded  as  to  degree  of  infestation 
according  to  the  system  already  described.  The  check  trees  aver- 
aged at  this  time  5.6  degrees  of  infestation,  estimated  on  a  scale  of 
six  degrees.  Those  of  the  experimental  plot,  on  the  other  hand, 
averaged  1.2  degrees — a  difference  of  4.4  degrees  in  favor  of  the 
experimental  plot,  or  a  ratio  of  benefit  of  79  per  cent.*  In  other 
words,  the  number  of  living  San  Jose  scales  on  this  experimental 
plot  was  virtually  one  fifth  that  which  would  have  been  present  Sep- 
tember 10  if  no  treatment  had  been  applied. 

Finally,  if  we  compare  the  condition  of  this  experimental  plot 
September  10  with  the  condition  of  the  same  plot  January  3,  when 
the  trees  were  first  inspected,  we  find  that  the  September  infestation 
averages  just  one  half  that  of  January. 

2.  This  was  also  a  lime  and  sulphur  mixture,  differing  from  the 

*To  ascertain  this  ratio,  the  figures  denoting  the  infestation  of  the  experimental 
plot  are  subtracted  from  those  of  the  check  plot,  giving  4.4  per  cent,  as  the  difference, 
and  this  divided  by  5.6,  the  measure  of  infestation  of  the  check  trees,  gives  79  per  cent. 


248  BULLETIN  No.  107.  [Apt-U. 

preceding  especially  in  the  fact  that  21  pounds  of  lime  and  18 
pounds  of  sulphur  were  used  to  50  gallons  of  water.  The  method 
of  preparation  was  virtually  the  same. 

Sixty-six  trees,  in  four  rows  running  across  the  end  of  the  less- 
infested  orchard,  II.,  were  treated  March  22  with  one  hundred  gal- 
lons of  the  spray.  At  a  general  inspection  made  May  27,  this  plot 
was  reported  as  in  favorable  condition,  with  very  few  living  scales, 
and  none  of  them  young.  Examined  September  10,  the  average  in- 
festation was  figured  at  1.36  degrees,  which,  compared  with  the  infes- 
tation of  the  two  central  rows  of  the  check  plot,  gives  a  benefit  of 
76  per  cent,  as  a  consequence  of  the  treatment.  Compared  with  its 
own  average  infestation  of  the  preceding  January,  we  find  this  plot 
improved  about  44  per  cent. ;  that  is  to  say,  the  degree  of  September 
infestation  is  approximately  56  per  cent,  that  of  the  preceding  Janu- 
ary. In  the  check  plot,  with  which  this  is  to  be  compared,  the  Sep- 
tember infestation  was  nearly  two  and  a  half  times  that  of  January. 

3.  This  is  a  simple  lime  and  sulphur  mixture  like  No.  i  of  this 
series,  the  ingredients  being  in  the  same  proportions  of  15  pounds 
each  of  lime  and  sulphur  to  50  gallons  of  water,  and  differing  merely 
in  the  method  of  preparation.     In  this,  the  lime  was  first  slaked  in 
10  gallons  of  water  where  50  gallons  of  the  spray  were  to  be  pre- 
pared, the  sulphur  was  then  stirred  in  dry,  and  the  whole  was  cooked 
from  30  to  40  minutes. 

One  hundred  and  one  trees  of  Orchard  II.  were  sprayed  March 
22  with  one  hundred  and  forty  gallons  of  the  solution.  As  this  plot  of 
six  rows,  running  the  whole  width  of  the  orchard,  lay  immediately 
beside  the  check,  the  average  September  infestation  of  the  two 
rows  adjoining  the  check  was  notably  greater  than  that  of  the  re- 
maining four  rows.  For  the  first  two  rows  it  averaged  1.9  degrees, 
and  for  the  remaining  four  rows,  1.44 — an  excess  of  32  per  cent,  of 
infestation,  apparently  due  to  the  proximity  of  the  check  and  the 
consequent  spread  of  the  young  from  those  heavily  infested  trees. 
On  this  account  the  two  inner  rows  of  17  trees  each  were  rejected, 
and  the  four  rows  remaining  were  compared  with  the  two  central 
rows  of  the  check  plot  itself. 

Comparing  the  1.44  degrees  of  infestation  of  the  experimental 
trees  with  the  5.6  of  the  rows  used  as  checks,  we  have  a  benefit  of  74 
per  cent,  resulting  from  the  treatment.  Or,  if  we  choose  to  compare 
the  September  condition  of  the  plot  with  that  of  January — again 
omitting  the  rows  nearest  the  check — we  find  a  difference  of  38  per 
cent,  in  favor  of  the  September  condition. 

4.  This   was  the  so-called   "California  wash,"    containing   15 
pounds  each  of  lime,  sulphur,  and  salt,  to  50  gallons  of  water. 


1906.]  EXPERIMENTS  WITH  SAN  JOSE  SCALE.  249 

Thirty  pounds  of  sulphur  was  first  stirred  into  20  gallons  of  boiling 
water,  and  30  pounds  of  lime  was  added.  The  mixture  was  then 
boiled  for  thirty  minutes,  with  constant  stirring,  after  which  30 
pounds  of  salt  was  added  and  the  boiling  was  continued  for  15  min- 
utes more.  The  mixture  was  then  diluted  with  water  to  form  one 
hundred  gallons,  and  applied  March  21  to  66  trees  of  Orchard  II., 
standing  in  four  rows  at  a  considerable  distance  from  the  check. 

Examined  May  29,  this  plot  was  reported  to  be  in  excellent  con- 
dition, with  but  few  living  old  scales  and  scarcely  any  young.  Of 
100  scales  taken  at  random,  15  were  alive — a  ratio  which,  however, 
would  have  but  little  significance,  two  months  having  elapsed  since 
the  trees  were  sprayed.  On  a  visit  to  these  trees  made  September  10, 
this  plot  showed  an  average  of  1.8  degrees  of  infestation,  cor- 
responding to  a  benefit  of  68  per  cent,  as  compared  with  the  condi- 
tion of  the  check  at  the  time.  If  the  comparison  be  made  with 
the  January  condition  of  the  same  plot,  the  September  condition 
shows  a  gain  of  37  per  cent. 

5.  This,  like  the  preceding  number,  is  a  "California  wash,"  but 
with  21  pounds  of  lime,  18  pounds  of  sulphur,  and  5  pounds  of  salt, 
to  50  gallons  of  water.    It  was  prepared,  like  the  preceding  mixture, 
by  pouring  the  sulphur  into  the  water  first,  and  following  with  the 
lime. 

It  was  applied  March  22  to  49  trees  standing  in  three  rows  of 
Orchard  II.,  seven  rows  intervening  between  this  plot  and  the  check. 
May  29,  scattering  full-grown  females  were  seen,  but  young  were 
extremely  few.  Only  7  were  found  on  5  trees.  The  bark  was  still 
covered  with  an  even  whitish  coat  at  this  date — two  months  after 
spraying.  Of  148  scales  examined,  20  were  alive.  On  September  10 
the  average  infestation  was  estimated  at  1.9  degrees,  which,  com- 
pared with  the  check  rows,  gave  a  benefit  ratio  of  67  per  cent.  That 
is,  the  scales  alive  on  these  trees  were  approximately  one  third  the 
number  which  the  trees  would  have  borne  if  they  had  not  been 
treated  the  preceding  March.  Compared  with  the  January  esti- 
mate, the  September  infestation  was  about  25  per  cent.  less.  In 
other  words,  the  effect  of  the  spray  up  to  this  time  had  been  to 
counterbalance  the  increase  of  the  scale  by  multiplication,  and  to  re- 
duce the  original  number  by  one  fourth. 

6.  The  usual  "California  wash,"  made  with  15  pounds  each  of 
lime,  sulphur,  and  salt,  to  50  gallons  of  water,  the  lime  being  first 
slaked,  and  the  sulphur  added  in  the  form  of  a  paste.    The  mixture 
was  then  boiled  for  30  minutes,  and  the  salt  was  added  and  the 
whole  boiled  1 5  minutes  more. 

Sixty-eight  trees  of  Orchard  II.  were  treated  March  21.    They 


250  BULLETIN  No.  107.  [April, 

were  in  four  rows  running  across  the  orchard  near  one  end,  and  far 
removed  from  the  check.  May  29  a  few  old  living  scales  were  found 
on  half  a  dozen  trees,  but  no  young,  either  crawling  or  newly  set. 
The  bark  of  some  of  these  trees  was  still  covered  with  innumerable 
dead  scales.  September  10  the  scales  remaining  had  multiplied 
somewhat,  giving  an  average  infestation  of  2.  degrees,  and  showing 
a  benefit  of  64  per  cent.  Compared  with  the  condition  of  the  trees 
in  January,  at  which  time  the  infestation  was  estimated  at  33  per 
cent,  per  tree,  the  September  condition  showed  an  improvement  of 
38  per  cent. 

7.  These  trees,  unlike  all  the  preceding,  were  in  the  orchard 
originally  the  worse  infested  of  the  two  (Orchard  L),  its  check  plot 
averaging,  in  January,  3.3  degrees  of  infestation  when  that  of  the 
other  orchard  (II.)  averaged  2.2  degrees.  At  the  time  of  the  Sep- 
tember inspection,  however,  this  difference  had  more  than  disap- 
peared, the  infestation  of  these  two  orchards  being  now  4.94  for 
Orchard  I.  and  5.36  for  Orchard  II.  That  is  to  say,  the  infestation 
of  the  orchard  worse  infested  in  January  had  increased  by  49  per 
cent,  while  that  of  the  less-infested  had  increased  by  145  per  cent. 
The  reasons  for  this  difference  were  not  clear.  The  September  infes- 
tation of  the  check  plot  in  Orchard  I.  was  practically  uniform,  show- 
ing no  invasion  from  the  adjoining  plots,  and  I  have  used,  for  com- 
parison, the  averages  for  the  whole  of  it  instead  of  those  for  the 
two  central  rows  only,  as  in  Orchard  II. 

This  experiment  was  a  January  treatment  of  141  trees,  some 
peach  and  some  apple,  with  the  "Oregon  wash"  made  of  15  pounds 
each  of  lime  and  sulphur,  and  il/2  pounds  of  blue  vitriol,  to  50  gal- 
lons of  water.  Two  hundred  gallons  of  the  wash  were  used  Janu- 
ary 3  and  twelve  gallons  more  the  following  day.  The  temperature 
of  January  3  was  but  a  few  degrees  from  freezing,  part  of  the  time 
above  and  part  of  the  time  below.  The  ground  was  covered  with 
snow,  and  light  winds  blew  from  the  north  and  northwest.  Janu- 
ary 4  the  temperature  fell  nearly  to  zero,  and  the  wind  shifted  to 
the  south. 

The  solution  was  prepared  by  the  process  commonly  used  in 
all  our  recent  orchard  work,  the  lime  being  first  placed  in  water 
which  had  been  heated  to  the  boiling  point,  and  the  sulphur  paste  in- 
troduced while  the  lime  was  slaking.  The  mixture  was  boiled  for 
30  to  40  minutes,  and  the  blue  vitriol,  previously  dissolved,  was 
added  and  the  whole  boiled  for  5  minutes  more.  All  of  the  trees 
were  thoroughly  sprayed,  and  but  few  tips  of  twigs  or  patches  of 
bark  could  be  found  not  covered  bv  the  residue  after  the  fluid  had 


1906.']  EXPERIMENTS  WITH  SAN  JOSE  SCALE.  251 

evaporated.     During  the  colder  part  of  these  days  the  spray  froze 
as  soon  as  it  touched  the  bark. 

May  26,  964  scales  were  examined,  of  which  773  were  dead,  and 
191,  or  20  per  cent.,  alive.  May  29  a  general  inspection  of  this  plot 
showed  many  living  scales,  young  and  old,  both  decidedly  more  abun- 
dant on  the  apple  than  on  the  peach.  Fifty  young,  for  example, 
were  found  in  one  square  inch  of  the  under  surface  of  a  twig  two 
inches  in  diameter,  and  on  another  eoual  area  no  were  counted. 
Traces  of  the  winter  spray  were  still  visible  on  the  trees.  Septem- 
ber 5  the  average  infestation  was  estimated  at  2.4  degrees,  which, 
compared  with  the  4.94  of  the  check  plot  for  this  orchard,  gave  a 
benefit  ratio  of  51  per  cent.  If  the  September  condition  of  these 
trees  is  compared  with  that  of  January,  a  gain  of  23  per  cent,  is 
found. 

8.  This  is  a  companion  experiment  to  No.  6,  the  same  prepara- 
tion being  used,  in  the  previous  case  in  March  and  in  this  case  in 
January.  It  was  the  usual  "California  wash"  of  15  pounds  each  of 
lime,  sulphur,  and  salt,  to  50  gallons  of  water.    It  was  sprayed  Jan- 
uary 10  upon  three  rows  of  peaches,  47  trees  in  all,  in  Orchard  II. — 
a  plot  immediately  beside  No.  6.     The  temperature  ranged  from 
10°  to  12°  above  zero,  and  snow  was  falling,  with  a  northeast  wind. 
The  spray  froze  as  it  struck  the  trees. 

At  the  inspection  of  the  29th  of  May  this  plot  was  reported  as  in 
very  unfavorable  condition,  many  young  scales  being  found  on  4 
trees  examined.  September  10  the  infestation  of  this  plot  averaged 
3.1  degrees — to  be  compared  with  5.6  of  the  check  plot  of  its  or- 
chard. This  gives  a  benefit  of  45  per  cent,  as  compared  with  the 
September  check,  or  of  12.5  per  cent,  if  compared  with  its  own 
January  condition. 

9.  This  is  an  experiment  with  the  "Oregon  wash,"  20  pounds 
of  lime,  15  pounds  of  sulphur,  and  il/2  pounds  of  blue  vitriol,  to 
50  gallons  of  water.     It  was  agplied  to  a  plot  of  eight  rows  in  Or- 
chard I.  containing  126  trees,  only  five  rows  of  which,  containing 
78  trees,  were  used  for  comparison,  owing  to  an  apparent  contami- 
nation of  three  rows  from  the  check  plot  adjoining.     These  trees 
were  sprayed  January  3  to  5,  the  temperature  ranging  from  28°  to 
36°.    Two  hundred  and  sixty-two  gallons  were  used,  the  most  of  it 
January  4. 

One  thousand  and  ten  scales  taken  at  random  from  12  trees  were 
examined  in  this  orchard  May  27,  and  26  per  cent,  were  found  alive. 
Generally  speaking,  however,  the  condition  of  the  orchard  was  re- 
ported as  extremely  favorable.  Most  of  the  insects  found  were  on 
the  higher  twigs,  which  were  less  heavily  coated  with  the  residue 


252  BULLETIN  No.  107.  [April, 

of  the  spray  than  were  the  larger  branches  and  the  trunk,  and  the 
greater  part  of  the  living  scales  were  found  on  such  twigs.  They 
were,  as  before,  more  abundant  on  the  apple  than  on  the  peach. 
September  5  the  average  infestation  of  the  78  trees  available  for 
comparison  was  figured  at  2.9  degrees,  which,  compared  with  the 
4.9  of  the  check  plot,  gives  a  benefit  of  42  per  cent,  from  this  Janu- 
ary treatment  with  the  "Oregon  wash."  As  compared  with  its 
own  January  condition,  this  plot  had  been  improved  by  12  per  cent. 

10.  A  January  spray  of  a  lime  and  sulphur  mixture  made  with 
soda — 30  pounds  of  lime,  15  of  sulphur,  and  5  of  soda,  to  50  gallons 
of  water.    The  mixture  was  prepared  January  4  as  follows : 

Thirty  pounds  of  Marblehead  lime  was  slaked  in  12  gallons  of 
water,  the  sulphur  being  added  in  the  form  of  a  paste  during  the 
slaking  process.  The  soda  was  added  in  three  lots,  the  first  about 
5  minutes  after  the  lime  began  to  slake,  and  the  others  at  intervals 
of  2  or  3  minutes.  The  mixture  was  then  stirred  for  10  minutes, 
diluted  with  cold  water  to  make  50  gallons,  no  boiling  being  neces- 
sary, and  applied  to  127  trees  in  Orchard  I. — a  plot  of  eight  rows 
immediately  beside  the  check.  The  temperature  was  a  little  above 
or  a  little  below  freezing,  a  strong  wind  blowing  from  the  south. 
There  was  no  appearance  of  any  increased  infestation  on  the  side 
nearest  the  check  plot,  and  the  averages  for  all  these  rows  are  conse- 
quently used  for  comparison. 

May  27,  scales  were  quite  numerous  on  this  plot,  including  both 
well-grown  females  and  some  young.  Of  676  examined,  30  per 
cent,  were  found  alive.  On  the  check  plot  at  the  same  time,  of  1200 
scales  examined,  39  per  cent,  were  alive.  September  5,  when  the  in- 
festation of  this  plot  was  finally  graded,  it  was  found  to  average 
3.37  degrees,  less  by  some  23  per  cent,  than  the  infestation  of  the 
check  plot  in  this  orchard.  Compared  with  its  own  January  condi- 
tion, the  September  infestation  was  estimated  at  practically  15  per 
cent.  less. 

11.  This,  like  the  preceding,  is  a  lime,  sulphur,  and  soda  mix- 
ture, differing  in  the  smaller  proportions  of  lime  and  sulphur  and  in 
the  greater  amount  of  soda.  Sixteen  pounds  of  lime  and  8  each  of 
sulphur  and  soda  were  used  to  50  gallons  of  water.    In  the  prepara- 
tion of  this  solution  8  pounds  of  sulphur  paste  was  put  into  a  few 
gallons  of  boiling-hot  water,  8  pounds  of  caustic  soda  was  added 
to  this  and  stirred  until  the  sulphur  was  dissolved,  and  16  pounds 
of  lump-lime  was  then  put  in  and  stirred  until  completely  slaked. 
The  entire  process  required  about  15  minutes'  work. 

The  spray  was  applied  January  5  in  Orchard  I.  to  124  trees, 
about' equally  peach  and  apple,  the  temperature  varying  from  32°  to 


1906:] 


EXPERIMENTS  WITH  SAN  JOSE  SCALE. 


253 


54°  at  different  times  of  the  day.  The  plot  of  eight  rows  was  at  the 
end  of  the  orchard  and  consequently  well  removed  from  the  check. 

May  27,  these  trees  were  found  unusually  infested  as  compared 
with  others  treated  at  the  time.  Of  575  scales  examined,  159  were 
living — a  ratio  of  28  per  cent.  At  the  fall  inspection,  September  5, 
the  average  infestation  of  this  plot  was  rated  at  3.43,  giving  a  bene- 
fit of  19  per  cent,  for  the  treatment  if  compared  with  the  check,  or 
about  12  per  cent,  if  compared  with  its  own  January  condition. 

The  principal  data  of  the  foregoing  discussion  may  be  conveni- 
ently summarized,  for  further  consideration,  in  the  first  of  the  fol- 
lowing tables. 

I.    TABLE  OF  EXPERIMENTS  WITH  LIME   AND   SULPHUR  PREPARATIONS 
ON  PLOTS  OP  47  TO  141  TREES. 

(Arranged  in  order  of  benefit  from  treatment.) 


No.  of 
Exper. 

Insecticide 

Or- 
chard 

Trees 

Treated 

Sept. 
Infes- 
tation 
Degrees 

Sept. 
Bene- 
fit 
per 
cent. 

Cost 
per 
100 
Gals. 

Check  Plot 

I 

126 

4.94 

Check  Rows 

II 

34 

5.6 

1 

Lime  and  Sulphur* 

15  L.,  158.,  50  W. 

it 

51 

Mar.  22 

1.2 

79 

$  .84 

2 

Lime  and  Sulphur 

21L.,18  S.,50  W. 

" 

66 

(1            U 

1.36 

76 

1.03 

3 

Lime  and  Sulphurf 

15  L.,  15  S.,50  W. 

«t 

67 

((        It 

1.44 

74 

.84 

4 

California  wash* 

15  L.  ,168., 

15  salt,  50  W. 

it 

66 

"    21 

1.8 

68 

.94 

5 

California  wash 

21  L.,  18  S., 

5  salt,  50  W. 

it 

49 

"    22 

1.9 

67 

1.07 

6 

California  washf 

15  L.,  15  S., 

15  salt,  50  W. 

it 

68 

"    21 

2. 

64 

.94 

7 

Oregon  wash 

15  L.,  15  S., 

1.5B.  V.,50  W. 

I 

141       Jan.  3 

2.4 

51 

1. 

8 

California  wash 

15  L.,  15S.. 

15  salt,  50  W. 

IE 

47 

"     10 

3.1 

45 

.94 

9 

Oregon  wash 

20  L.,  15  S., 

1.5  B.V.,  50  W. 

I 

78 

Jan.  3-5 

2.9 

42 

1.07 

10 

Lime,  Sulphur  and  Soda 

30  L.,  15  S., 

5  soda,  50  W. 

•« 

127 

"      4 

3.37 

23 

1.44 

11 

Lime,  Sulphur  and  Soda 

16  L.,  8S., 

8  soda,  50  W. 

ii 

124 

"      5 

3.43 

19 

1.24 

*Sulphur  put  in  first,  lime  added. 
tLime  first,  sulphur  added. 


254 


BULLETIN  No.  107. 
RECAPITULATION. 


[April, 


Simple  lime  &  sulphur 

II 

184 

March 

1.33 

76 

California  washes 

u 

183 

M 

1.9 

65 

Oregon  &  California 
washes 

I&II 

266 

January 

2.8 

46 

6 

California  wash 

II 

68 

March 

2. 

64 

8 

«           <» 

(1 

47 

January 

3.1 

45 

Lime,  sulphur,  &  soda 

I 

251 

H 

3.4 

21 

II.    TABLE  OF  EXPERIMENTS  WITH  LIME  AND  SULPHUR  PREPARATIONS 

ON  PLOTS  OF  5  TO  12  TREES. 

No.  of 
Ex  per. 

Insecticide 

Or- 
chard 

Trees 

Treated 

Sept. 
Infes- 
tation 
Degrees 

Sept. 
Bene- 
fit 
per 
cent. 

Cost 
per 
100 
Gals. 

12 

Oregon  wash  with  Del. 
limoid.    20L.,15S., 

13 

1.5B.V.,  50  W. 
Oregon  wash  with  Wis. 
limate.  20  L.,  15  S., 
1.5B.V.,50W. 

I 

u 

11 
12 

Mar.  24 
"    23 

1.91 
2.08 

61 

58 

$1.07 
1.07 

14 

Oregon  wash  with  hy- 
drated  lime  No.  1. 

20  L.,  15  S., 
1.5  B.V.,  50  W. 

;t 

11 

"    24 

2.18 

56 

1.07 

15 

Oregon  wash  with  hy- 
drated  lime  No.  2. 

16 

20  L.,  15  S.. 
1.5  B.V.,  50  W. 
Calcothion. 

u 
it 

11 

5 

u       u 

"    22 

2.18 
2.3 

56 
55 

1.07 
5. 

17 

Con  Sol.  1  part  to  40. 

" 

9 

1(            11 

4.21 

15 

2.40 

III.    MISCELLANEOUS  EXPERIMENTS. 


No.  of 
Exper. 

Insecticide 

Or- 
chard 

Trees 

Treated 

Sept. 
Infes- 
tation 

Sept. 
Bene- 
fit 

Cost 
Eer 
DO 

Degrees 

per 
cent. 

Gals. 

18 

Scalecide 

I 

31 

Mar.  24 

2.57 

47 

$2.50 

19 

Whale-oil  soap 

2  Ibs.  to  the  gallon 

II 

117 

it      it 

1.9 

65 

8. 

20 

Tak-a-nap  soap 

1  Ib.  to  the  gallon 

I 

8 

it      it 

15 

5. 

1906.]  EXPERIMENTS  WITH  SAN  JOSE  SCALE.  255 

GENERAL  RESULTS  OF  THE  FOREGOING  ELEVEN  EXPERIMENTS. 

An  examination  of  the  column  of  the  preceding  table  showing 
percentages  of  "September  benefit"  for  the  various  kinds  of  treat- 
ment enables  us  to  divide  at  once  the  series  of  experiments  into  four 
groups — three  of  three  experiments  each,  and  one  of  two.  The  first 
six  experiments  were  all  made  in  the  same  orchard,  and  all  in  March. 
It  is  especially  interesting  to  see  that  the  first  three,  in  which  the  in- 
secticide was  a  simple  lime  and  sulphur  solution  without  salt  or  blue 
vitriol,  show  ratios  of  74  to  79  per  cent,  of  benefit,  with  an  average 
of  76.3,  while  the  next  three  experiments,  all  made  with  the  "Cali- 
fornia wash,"  the  composition  being  the  same  as  that  of  the  preced- 
ing three  except  that  salt  was  added,  give  ratios  of  benefit  ranging 
from  64  to  68  per  cent.,  with  an  average  of  65. 

These  experiments  strongly  indicate,  if  they  do  not  substantially 
prove,  that  the  addition  of  salt  to  the  lime  and  sulphur  is  a  detriment 
rather  than  a  benefit,  since  a  difference  of  17  per  cent.,  or  more 
than  one  sixth,  in  the  ratios  of  apparent  benefit,  under  conditions 
otherwise  so  uniform,  can  scarcely  be  accounted  for  in  any  other 
way. 

The  next  group  of  experiments,  7  to  9  of  our  series,  when  con- 
trasted with  Experiments  4  to  6,  show  a  difference  in  final  effect  of 
spring  and  midwinter  sprayings.  The  average  benefit  of  the  "Cal- 
ifornia wash"  applied  to  187  trees  in  March  was  65  per  cent.,  while 
that  of  the  Oregon  and  California  washes  applied  to  320  trees  iii 
January  was  46  per  cent. — a  difference  of  41  per  cent,  in  favor  of 
the  spring  treatment.  The  January  group  of  three  experiments  does 
not  compare  exactly  with  the  March  group  of  three,  since  two  of 
the  former  were  made  on  a  different  orchard  from  the  latter,  and 
were  made  with  the  "Oregon  wash"  instead  of  the  "California 
wash."  If,  however,  Experiment  8  be  compared  with  Experiment  6, 
in  which  all  the  conditions  were  identical  except  the  time  of  spray- 
ing, we  get  the  same  difference  of  ratios  of  benefit  as  before — 45  per 
cent,  for  the  January  treatment  and  64  per  cent,  for  the  March 
treatment. 

Furthermore,  the  last  two  experiments,  10  and  n  of  our  series, 
contrast  still  more  strongly  with  the  three  preceding,  giving  but  19 
and  23  per  cents  of  benefit,  with  an  average  of  21  per  cent,  as  com- 
pared with  46  per  cent,  for  the  preceding  group.  This  difference 
of  more  than  100  per  cent,  can  be  accounted  for  only  on  the  suppo- 
sition that  the  cold  solution  of  lime  and  sulphur  made  with  soda 
was  far  less  efficient  as  an  insecticide  than  the  ordinary  form  of 
Oregon  and  California  washes  made  by  boiling. 


256  BULLETIN  No.  107.  [April, 

One  additional  inference  may  be  $ra.wn  from  a  comparison  of 
Experiments  i  and  4  on  the  one  hand  with  3  and  6  on  the  other.  In 
each  of  the  former  pair  the  lime  was  slaked  in  water  in  which  the 
sulphur  had  been  first  stirred  up.  In  each  of  the  latter  pair  the  lime 
was  put  in  first,  and  the  sulphur  was  added  during  the  slaking  proc- 
ess. That  there  is  an  apparent  advantage  in  the  first  method  of 
preparation  is  shown  by  the  difference  of  5  degrees  of  benefit  be- 
tween Experiments  i  and  3,  and  4  degrees  of  benefit  between  Experi- 
ments 4  and  6.  It  thus  appears  that  solutions  made  by  stirring  the 
sulphur  into  the  hot  water  first  and  adding  the  lime  to  this  mixture, 
are  more  efficient  than  if  the  order  of  procedure  is  reversed. 

It  follows  from  this  discussion,  as  a  general  conclusion,  that 
simple  solutions  of  lime  and  sulphur  made  by  boiling,  without  salt 
or  blue  vitriol,  the  sulphur  being  added  to  the  water  first,  had 
much  the  best  insecticide  effect  in  these  orchards;  that  the  March 
spraying  was  nearly  twice  as  effective  as  the  January  spraying ;  and 
that  the  soda  solutions  of  lime  and  sulphur  made  without  heat  had 
a  final  efficiency  less  than  half  that  of  the  boiled  solutions  applied  at 
the  same  time. 

Minor  Experiments. — Six  experiments  with  other  lime  and  sul- 
phur mixtures  were  made  on  too  small  a  scale  to  compare  with  the 
eleven  preceding,  but  with  results  which  seem  to  me  worthy  of  rec- 
ord, particularly  as  they  are  fairly  uniform  for  this  group  of  insecti- 
cides notwithstanding  the  small  number  of  trees  used  in  each  ex- 
periment. 

From  5  to  12  trees  were  sprayed  with  various  forms  of  the 
''Oregon  wash,"  with  "Calcothion,"  and  with  "Con  Sol,"  all  in 
March  from  the  22d  to  the  24th,  and  all  in  Orchard  II.  Four  of  the 
insecticides  used  were  forms  of  the  "Oregon  wash"  made  with  dif- 
ferent brands  of  hydrated  lime  instead  of  ordinary  lump-lime  from 
the  kiln.  In  all  cases  20  pounds  of  the  lime,  15  pounds  of  sulphur, 
and  il/2  pounds  of  blue  vitriol  were  used  to  50  gallons  of  water,  the 
only  difference  being  in  respect  to  the  kind  of  lime,  the  so-called 
Wisconsin  "Limate"  being  used  in  one,  the  Marblehead  hydrated 
lime  in  two  others,  and  the  Delaware  "Limoid"  in  the  fourth.  These 
were  applied  in  each  case  to  n  or  12  trees,  and  the  effect  was  ascer- 
tained by  the  inspection  method  used  in  the  larger  experiments. 

The  resulting  benefits  ranged  from  56  to  6 1  per  cent.,  as  tested 
by  the  September  inspection,  using  the  September  condition  of  the 
check  plot  of  Orchard  II.  as  a  basis  of  comparison.  These  mixtures, 
with  their  average  benefit  of  58  per  cent.,  were  apparently  less  effi- 
cient than  the  California  washes  used  at  the  same  time,  which  give 
a  benefit  of  65  per  cent.  The  "Calcothion,"  applied  cold  without  di- 


1906.]  EXPERIMENTS  WITH  SAN  JOSE  SCALE.  257 

lution,  as  it  was  received  from  the  manuf acturers,  was  used  on  only 
5  trees,  with  a  ratio  of  September  benefit  figured  at  55  per  cent. — 
substantially  the  same  as  that  of  the  Oregon  washes  just  referred  to. 
"Con  Sol,"  diluted  with  water  at  the  rate  of  i  to  40,  and  applied  cold 
to  9  trees,  gave  a  ratio  of  only  15  per  cent,  of  benefit.  The  Oregon 
washes  cost  at  the  rate  of  $1.07  per  hundred  gallons  for  materials; 
"Con  Sol,"  $2.40;  and  "Calcothion,"  $5. 

It  may  be  provisionally  inferred  from  these  small  experiments 
that  neither  of  these  two  compounds  has  any  advantage  over  the 
better-known  washes  except  in  point  of  convenience,  and  this  must 
be  paid  for  by  a  considerably  higher  cost  than  that  of  the  lime  and 
sulphur  mixtures — more  than  twice  as  great  for  "Con  Sol,"  and 
nearly  five  times  as  great  for  "Calcothion." 

MISCELLANEOUS  ADDITIONAL  INSECTICIDES. 

Only  one  of  the  kerosene  insecticides  was  tried  on  a  number  of 
trees  sufficient  to  give  any  permanent  value  to  the  experiment. 
The  soluble  petroleum  compound  known  as  "Scalecide,"  applied 
March  24  in  a  5  per  cent,  mixture  with  water  to  3 1  trees  in  Orchard 
I.,  showed  a  September  infestation  of  2.6  degrees,  equivalent  to  a 
benefit  of  47  per  cent. — decidedly  less  than  that  of  any  of  the  lime 
and  sulphur  washes  used  in  March,  as  shown  by  Table  I.,  and  con- 
siderably less  than  that  of  the  Oregon  washes  of  Table  II.  It  seems  to 
belong,  in  insecticidal  effect,  with  the  Oregon  and  California  washes 
as  applied  in  January,  its  47  per  cent,  of  benefit  being  substantially 
the  same  as  the  46  per  cent,  of  the  latter  treatment.  Its  cost  was 
$2.50  per  hundred  gallons — essentially  the  same  as  "Con  Sol" — and 
its  benefit  was  three  times  as  great.  It  was  apparently  the  best  of 
the  ready-made  insecticides  tested  by  us  last  year. 

A  kerosene  preparation  known  and  sold  as  "Frutolin"  was  tried 
March  24  on  3  trees,  and  several  variations  of  a  20  per  cent,  kerosene 
mixture  made  with  water  and  hydrated  lime  in  lieu  of  soap  solution 
were  applied  on  the  same  day  to  5  more  trees,  all  in  Orchard  I. 
The  results  were  essentially  the  same  with  all  these  mixtures,  so  far 
as  one  can  judge  from  these  small  experiments.  The  trees  treated 
averaged  4  degrees  of  infestation  September  10,  giving  a  benefit 
ratio  of  19  per  cent,  as  compared  with  the  check  of  their  orchard. 
The  cost  of  the  "Frutolin"  mixture  was  $25.10  per  hundred  gallons, 
and  that  of  the  so-called  emulsions  made  with  kerosene  and 
lime  was  $1.07. 

Two  simple  soap  solutions  were  used,  whale-oil  soap  on  117 
trees,  and  "Tak-a-nap"  soap  on  8  trees,  the  former  in  Orchard  II. 


258  BULLETIN  No.  107.  [April, 

and  the  latter  in  Orchard  I.  The  whale-oil  soap  was  used  March  23 
and  24  in  the  ordinary  ratio  of  2  pounds  to  the  gallon  of  water  on  a 
plot  immediately  beside  the  check  plot  of  its  orchard.  As  the  row 
adjacent  to  the  check  showed  much  the  highest  infestation  of  any 
one  of  the  seven,  it  has  been  thrown  out  in  the  comparison. 

September  10  the  infestation  of  this  plot  was  reckoned  at  1.9  de- 
grees, which,  compared  with  that  of  the  check  plot  at  the  same  time, 
gives  a  benefit  ratio  of  65  per  cent. — making  this  solution  virtually 
the  equivalent  of  the  California  washes  made  with  salt,  as  shown  in 
Table  I.  Its  cost,  $8  per  hundred  gallons  of  the  solution — nearly 
eight  times  that  of  the  California  washes, — is  the  most  serious  ob- 
stacle to  its  general  use.  Except  for  its  occasional  destruction  of 
blossom  buds  of  the  peach  and  other  especially  sensitive  fruits,  it 
would  still  remain  the  most  desirable  for  use  on  a  small  scale.  For 
the  apple  orchard,  if  the  difference  in  expense  is  not  worth  consider- 
ing, it  is  to  be  recommended  as  among  those  next  in  efficiency  to  the 
simple  lime  and  sulphur  washes. 

,  "Tak-a-nap"  soap  dissolved  in  cold  water  at  the  rate  of  one 
pound  to  the  gallon,  and  applied  March  24  to  8  trees  in  Orchard  I., 
gave  an  apparent  September  benefit  of  15  per  cent.  The  cost  is  $5 
for  one  hundred  gallons. 

A  caustic-soda  solution  made  with  water  at  the  rate  of  i  pound 
to  6  gallons  and  applied  to  3  trees  March  24  produced  no  percep- 
tible effect,  these  trees  being,  in  fact,  worse  infested  in  September 
than  they  were  in  January,  and  even  worse  than  were  the  trees  of 
the  check  plot  at  the  September  inspection. 

Mention  may  also  be  made  of  Bowker's  Tree  Soap,  used  on  only  a 
single  tree,  but  there  apparently  with  very  good  effect.  It  was  ap- 
plied March  24  to  a  badly  infested  tree  in  Orchard  I.  at  the  rate  of 
2  pounds  of  soap  to  a  gallon  of  warm  water. 

At  the  time  of  the  May  inspection  100  scales  from  this  tree  were 
counted,  all  of  which  were  dead,  and  Mr.  Taylor  remarks  that  he 
could  not  find  a  scale  on  this  tree  alive,  though  he  scraped  and  ex- 
amined most  of  the  twigs  to  their  tips.  By  September,  however, 
this  tree  was  moderately  infested,  possibly  by  invasion  from  adja- 
cent trees  which  had  been  treated  with  kerosene  emulsion. 

This  soap  costs  jl/2  cents  per  pound  in  loo-pound  kegs,  bringing 
the  cost  of  the  spray  to  $15  per  hundred  gallons. 

COST  oV  MATERIALS  . 

The  cost  of  all  the  materials  contained  in  the  various  insecticides 
used  in  these  experiments  is  shown  in  the  last  column  of  the  tabular 


1906  ]  EXPERIMENTS  WITH  SAN  JOSE  SCALE.  259 

summaries,  with  the  exception  of  those  used  in  certain  minor  experi- 
ments, which  have  been  separately  given.  This  cost,  stated  in 
terms  of  one  hundred  gallons  of  the  spray  diluted  and  otherwise 
made  ready  for  actual  distribution,  is  based  on  the  following  rates 
for  materials,  which  are  those  actually  paid  by  us,  or,  in  a  few  minor 
cases,  those  furnished  us  by  the  manufacturers.  None  of  these 
prices  includes  freight. 

Lime.     90  cents  per  bbl.  of  196  Ibs. 
Sulphur.     $2.30  per  cwt.,  bought  in  ton  lots. 
Salt.     33  cents  per  cwt.,  by  the  bbl. 
Blue  vitriol.     $6  per  cwt. 
Caustic  soda.     $4.50  per  cwt.,  in  10-lb.  cans. 
Whale-oil  soap.     4  cents  per  lb.,  by  the  bbl. 
Tak-a-nap  soap.     5  cents  per  lb.,  in  40-lb.  packages. 
Kerosene.     12%  cents  per  gal.,  by  the  bbl. 
Marblehead  hydrated  lime  No.  I.     50  cents  per  cwt. 
"  "  "       "    2.     50  cents  per  cwt. 

Wisconsin  limate.     50  cents  per  cwt. 
Delaware  limoid.     Highest  grade,  $5.  per  bbl.  of  200  Ibs.;  cheaper 

grade,  $2.50  per  bbl.,  or  $14.  per  ton. 
Calcothion.     5  cents  per  gal.,  if  bought  by  the  bbl. 
Con  Sol.    $1.  a  gal. 
Frutolin.     66  cents  per  liter  (1.06  quarts)  in  cases,  each  containing  a 

dozen  liter  cans. 
Scalecide.     50  cents  per  gal.,  in  50-gal.  bbls. 

The  cheapest  of  these  washes,  counting  cost  of  materials  only,  is, 
fortunately,  the  one  found  most  efficient  in  these  experiments, 
namely,  the  simple  lime  and  sulphur  wash  in  the  ratio  of  1 5, 1 5, 50,  and 
costing  84  cents  per  100  gallons  when  ready  for  spraying.  The  next 
in  order  is  the  common  "California  wash"  of  lime,  sulphur,  and  salt 
(15,  15,  15,  50),  costing  94  cents  per  hundred  gallons.  The  "Ore- 
gon wash"  made  by  the  old  formula  still  in  most  general  use,  and 
containing  15  pounds  of  lime,  15  pounds  of  sulphur,  and  il/2  pounds 
of  blue  vitriol  to  50  gallons  of  water,  costs  $i  per  hundred  gallons; 
and  the  simple  lime  and  sulphur  mixture  with  21  pounds  of  lime 
and  18  pounds  of  sulphur  to  50  gallons,  costs  $1.03.  The  "Oregon 
wash"  with  the  lime  (of  whatever  form)  increased  to  20  pounds, 
amounts  to  $1.07  per  hundred  gallons;  and  the  lime  and  soda 
washes,  from  $1.24  to  $1.44,  dependent  upon  the  proportions  of  the 
ingredients  as  given  in  Table  I.,  Experiments  10  and  n. 

The  next  in  order  of  cost  is  "Con  Sol,"  at  $2.40  per  hundred  gal 
Ions,  i  part  of  the  insecticide  to  40  of  water;   and  then  "Scalecide," 
$2.50  per  hundred  gallons,  when  used  in  a  5  per  cent,  solution.    The 
kerosene  emulsions  made  with  hydrated  lime  and  diluted  to  contain 


260  BULLETIN  No.  107.  [April, 

20  per  cent,  of  kerosene,  cost  $3.62  for  a  hundred  gallons  of  the 
diluted  mixture.  "Tak-a-nap"  soap,  a  pound  to  the  gallon,  costs  $5 
a  hundred  gallons,  and  the  ordinary  solution  of  whale-oil  soap,  $8 
for  the  same  amount.  "Frutolin"  costs  $25.10  per  hundred  gallons 
when  diluted  with  9  parts  of  water  to  i  of  "Frutolin,"  as  advised 
by  the  manufacturers. 

GENERAL  SUMMARY. 

i.  The  cheapest  and  most  efficient  of  the  eleven  insecticide  mix- 
tures thoroughly  tested  against  the  San  Jose  scale  were  the  simple 
lime  and  sulphur  mixtures  (without  salt  or  blue  vitriol)  dissolved  by 
boiling  together.  They  cost,  for  materials,  from  84  cents  to  $1.03  per 
hundred  gallons  of  the  fluid  spray,  varying  according  to  the  propor- 
tions of  the  chemicals  used.  Infested  trees  treated  with  these  solu- 
tions in  March,  bore  about  one  fifth  as  many  scales  the  following 
September  as  companion  trees  not  treated. 

2.  The  next  in  value  was  the  "California  wash"  made  with 
lime,  sulphur,  and  salt,  at  an  expense  of  94  cents  to  $1.07  per  hun- 
dred gallons,  and  the  "Oregon  wash"  of  lime,  sulphur,  and  blue 
vitriol,  costing  virtually  the  same. 

3.  There  was  a  marked  and  very  important  difference  in  the 
final  effect  of  these  washes  and  mixtures,  dependent  upon  the  time 
of  their  application,  the  midwinter  treatment  yielding  a  result  far 
inferior  to  that  of  early  spring. 

4.  The  cold  solution  of  lime  and  sulphur  made  with  soda  was 
found  less  than  one  third  as  effective  as  the  washes  dissolved  by 
boiling.     Its  materials  were  also  somewhat  more  costly,  varying, 
according  to  the  proportions  of  the  ingredients,  from  $1,24  to  $1.44 
per  hundred  gallons. 

5.  The  petroleum  preparation  known  as  "Scalecide,"  which  has 
the  advantage  that  it  may  be  prepared  for  use  by  simply  diluting 
with  water,  was  found  somewhat  less  efficient  than  the  lime  and  sul- 
phur mixtures,  and  cost  about  2^2  times  as  much  as  the  raw  mate- 
rials of  those  preparations. 

6.  Whale-oil   soap  compared  very  well   with  the   "California 
wash,"  but  at  a  cost  approximately  eight  times  as  great. 

7.  Less  confident  statements  may  be  made  with  reference  to  Ore- 
gon washes  made  with  hydrated  lime,  and  to  the  commercial  insecti- 
cides known  as  "Con  Sol"  and  "Calcothion,"  experiments  with  these 
substances  having  been  made  on  too  small  a  scale  to  warrant  final 
conclusions.    They  strongly  indicate,  however,  that,  with  the  excep- 
tion of  "Con  Sol,"  these  mixtures  have  an  insecticide  value  some- 


1906.]  EXPERIMENTS  WITH  SAN  JOSE  SCALE.  261 

what  less  than  that  of  the  ordinary  "Oregon  wash."  "Calcothion" 
is  applied  as  received,  without  either  additional  preparation  or  dilu- 
tion. It  has  the  disadvantage  of  a  high  cost,  amounting  to  $5  per 
hundred  gallons. 

8.  Minor  experiments  with  several  additional  insecticides  are 
briefly  described  on  pages  256  and  257. 

9.  The  expense  of  preparation  of  the  mixtures  to  be  dissolved  by 
boiling  is  so  variable,  according  to  the  amount  to  be  used,  the  sup- 
ply of  available  labor,  and  the  kind  and  cost  of  fuel,  that  no  attempt 
has  been  made  to  estimate  it.   For  all  the  lime  and  sulphur  solutions 
except  those  made  with  soda,  and  for  whale-oil  soap,  it  amounts  vir- 
tually to  the  cost  of  boiling  successive  quantities  of  fifty  gallons  of 
water,  each  for  30  to  45  minutes. 


'          -     •  "&  sf^^      I    — mm**r      A     m,-^l  ^~\.  t>-^         -:vT      "^^i  <s-^        » 


